The Virus Core (Core B) will be responsible for providing overall scientific support to the Investigators participating in this Program. The Specific Aims of the Core are: 1. To generate, catalog, and provide large sucrose gradient-purified stocks of both wildtype and recombinant vaccinia viruses as requested by our Program Project Investigators, 2. To provide mice before or after infection with wildtype or recombinant vaccinia viruses, harvest specific tissues from the mice, and to perform the initial processing of these samples (including determination of virus load) as requested, and 3. Infect mock-treated or mice with airway hyperreactivity transferred from Core C with vaccinia virus, and perform initial processing and analysis of specific tissues at varioustimes post-infection. An advantage of this Scientific Core is that it will centralize the key elements of the Program in the context of infection: viruses, animals, and tissue harvesting with initial processing of organs from infected mice, all under one roof, and has already been in place for the past five years. The distribution of resources amongst the different projects is coordinated with the individual Project Directors, so that the most efficient use of the resources will be achieved. Thus, the Virus Core is the foundation from which the highly interactive and well-linked projects of the Program will be able to achieve their goala better understanding of the immunopathogenesis of vaccinia virus in the lung and other tissues. The knowledge thus gained from these studies can be applied to other poxviruses as well, such as variola virus. RELEVANCE (See instructions): Core B is a supportive laboratory for resources to be used by investigators in the Program. As such, it will facilitate the Program's ability to discover how the immune system responds to a virus infection, thereby providing information that can be applied to the development of new and more effective vaccines.